Arc-light carbon.



H. AYRTON. I ARC LIGHT CARBON. APPLICATION FVILED SEPTJB. 1914.

1,261,891. Patented A 9,1918.

2 SHEET EET l.

Figa.

n L"f Nk\\\\\\\\\\\\\\\\\ H.AYRTON.

ARC LIGHT CARBON.

APPLICATION FILED SEPT. 2s. 1914.

1,261,891. i Patented .9,1918...

2 SHEET EET 2.

jug 4.,

IWW

figc

mmm

mm Lf? INVENTOR :4

WITNESSES; M l By Attorneys,

mma AYn'roN, or HYDE` rank, LONDON, ENGLAND.

ARC-LIGHT CARBON.

Specification of Letters Patent.

Patented Apr. e, 191e.

Application filed September 28, 1914. Serial No. 863,894. l

To all whom t may camera:

Be it known that I, HERTHA AYR'roN, a

f subject of the King of Great Britain, residing at 41 Norfolk Square, Hyde Park, in

.the cityvand county of London, England,

have invented certain new and usefulImprovements in Arc-Light Carbons,of which the following is a specication.

rIhis invention relates to negative arc light carbons and has for its object to progide an improved construction'of such carons.

I have previously published the results of .certain experiments of blowing air and certain gases into the arc through holes bored throu h positive and negative carbons.

It as further been proposed to employ various constructions of hollow or tubular carbons where the walls of the tube were divided up to form a circle of individual carbons giving during burning a series of arcs, and in another case a tubular carbon was so yarranged that the arc rested on one part of the annulus and by rotation of the carbon fresh parts of the annulus were presented to the arc and consumed.

After an extensive investigation I find i that results far superior to anything hithervet to produced both in steadiness of burning and regularity of consumption between positive and negative carbons and in general utilit are obtained by the employment of a ho ow negative carbon covered with a thin film of copper or other suitable material less combustible than the carbon. Suitable means are provided to prevent the passage of air through the hole to the arc.

I have previously proposed to employ a l copper covering for another kind of carbon me serves as a means for predeterminlng" or adjusting the rate at which the hollow carbons will burn away.

The said copper covering forms a tightly adhering incombustible skin over the -carbon which, while protecting the major portion of it from burning, always melts off and volatilizes at such a distance from the tip as to insure that the tip of the carbon shall be tapered to the right length for the carbonto burn away at the rate required. I nd that the thickness of the copper skin may be varied with advantage within certain limits. y

rIhe lower of these limits is determined .by the thickness required to withstand the necessary handling and packing, the upper limit depends upon the thickness which will result in the tip of the carbon burning away with suficient steepness to insure steadiness ofthe arc.

Within these limits quite a small variation in the thickness of the metallic skin makes a sucient variation in the length of the carbon tip exposed to cause a considerable change in the rate of burning of the carbon. Increasing the thickness of the copper makes the carbonl burn with a shorter blunter point and therefore more slowly, while diminishing the thickness of copper makes it burn with a longer and more tapering point and rtherefore more quickly.

I nd that by choosing the right size of carbon and hole, and the right thickness of copper skin, it is always possible to obtain a hollow negative carbon that will burn steadily at substantially the same rate as any positive carbon suitable for the current and pressure employed, and, moreover, these results will be obtained in any of the various types of lamphouse usually employed.

ther metals besides copper may be employed to lform the incombustible coating although copper has so far .been found the most'useful.

In a negative carbon made in accordance with the, present invention and having a central hole it is also important that the said hole should beof such dimensions relatively tothe size of the carbon, that 4.during burning, the yarc completely surrounds the hole, which is encircled by a flat surface from the outer edge of which the carbon tapers steeply away. Whenthe hole 1s partially filled with a pencil of carbon theat surface is not sogapparent.

I nd that with a negative carbon of 12 lil:

millimeters diameter coated with a iilm or copper about .04C millimeter in thickness and having a hole of 2 millimeters diameter leaving walls oi 5 millimeters thickness, ex- 5 cellent results are obtained in an open direct current arc when used with a cored positive carbon and a current of 85 amperes.

"W hat is usually employed in the ordinary cinematograph lamphouse is a negative carle bon (not coppered) ot 18 mm. diameter tor the same current-85 amperes.

'lhe cross sectional area of my new negative carbon is less than one halt that oi the ordinary negative carbon.

This advantage is maintained in all sizes but in varying degrees.

One great advantage arising trom the comparatively small cross sectional area is that in use the shadow is lessened and there 2o are general advantages in the cost ot manufacture and transport.

is is well understood the positive carbon has to be selected according to the amount of current and pressure. Any positive carbon may be used with my invention.

Referring to the accompanying drawings which show further examples oi carbone made according to this invention Figure l is a view in longitudinal section su ot one torna of carbon.

Fig. 2 is a view in longitudinal section of another form ci carbon.

llig. 3 is a view showing an example ci the manner in which a pair of carbons burn away in use.

lligs. e and 5 show modified constructions.

ln the example shown in Fig. l, the

negative carbon a has a central hole b,

which, however, does not extend completely, 4o through the carbon, one end a of which is solid. The other end a2 of the carbon, where the arc is formed, is shown as slightly tapered and iinished oli2 obliquely, this being the shape which such a carbon assumes in use when disposed at an angle in relation to the positive carbon for example as in +`ig.8. W hen the carbons are disposed in alinement the tip of the carbon will be flat instead or" oblique. A thin tilm or coatoo ing c ot copper is applied to the exterior surface.

ln some cases a pencil ot carbon may be located in the hole in such manner as to leave a suitable longitudinal space.

F ig. 2 shows an example of this lrind oi` carbon and comprises the portion a having a central hole closed at the end a and a centrally disposed pencil ot' carbon CZ, of less diameter than the inside diameter ot the c@ said central hole is located in the hole h.

lt will be seen by reference to the drawings, particularly Fig. 2, that the pencil Z is not in surface engagement with the inner surface ci the hollow tubular body a and ce that there is considerable space between the two. This carbon is coated with a oi copper or other meta-l or other suitable material less combustible than the carbon; The

tip a2 of this carbon may be shaped as v shown in the drawing or it may he shaped to my other appropriate form. llt required the inner pencil oi carbon may be coated with copper or other metal. g

l am aware that it has hitherto been proposed to copper the cores or cored carbone.

, llig. 3 shows the oblique shape of the end of a negative carbon a, such as shown in Fic'. l, and the position which the oblique surface assumes relatively to the positive carbon p, in use when the said carbons are disposed in the angular position shown. 'llhis view also shows the position normally occupied by the are itself.

ln the improved carbon the hole may in some cases be quite small relatively to the thickness ot the walls.

Any suitable means other than described may be employed for closing the hole to prevent the air passing therethrough to the are, for example, the hole may be closed by external means such as a part of the holder or a projection thereonn Although l have fully herein set iortl` what l have found from experiment to give the beneioial results referred to, it is to be understood that the claims are not to be restricted to the use ci? the particular thickness or copper mentioned as there may be circumstances in which a greater thickness oi copper may he employed with advantage, and my claims are to include a hollow carbon with any suitable thickness of copper coating or with a coating of other metal less combustible than the carbon and proportioned to give the specied eidects and iurther if required, when a pencil of carbon is iitted into the hollow as in vFig. 2, said pencil may be covered with copper or other metal in the manner usual with cores.

According to a modilication ozt'the invention, shown in ll ig. e as applied to a carbon constructed as in lig. i., the hole or holes ot the hollow carbon are iilled or charged as indicated at e with some substance which will burn away or melt so as to leave the tip oi the carbon or a suitable length near the tip hollow or recessed to such a distance as will give the results ot a hollow carbon such as herein set forth. i .l

As an example the lling or charging may consist ot silicate ot soda in some convenient 'form although any other suitable material may be employed l ln this way the cartoon may be said to be a cored carbon which will be hollow tor the whole or part ot its length during burning or aiter being put into use.

"W hen a pencil oi carbon is employed in the hole as in llig. 5 or holes it may be held m position hy or the space between it and the walls of the hole may be filled with material e which easily melts or burns away in the lmanner hereinbefore set forth. What I claim and desire to secure by Letters Patent is:

L An arc light carbon comprising a hollow tubular body open at the arc end and closed at the other end to prevent the passage of air, the carbon cylinder beingof uniform thickness throughout that part which is to be burnt, said body having upon its outer surface a lilm of metal less combustible than the carbon and of a predetermined thickness, for regulating the speed of burning of the said carbon.

2. An arc light carbon as claimed in claim' -the saidl carbon, and a pencil of carbon of less diameter than the inside diameter of the said tubular body, and disposed therein,

`1 characterized in that the hollow part is the outersurface of the said pencil having a film of metal less combustible than the carbon of said pencil and of a predetermined thickness for regulating the speed of burning Vof the said carbon.

4. An arc light carbon as claimed in -claim illed with a material adapted to be removed by the heat of the arc, so as to leave a suita le length of the carbon` near the tip hollow to such a distance as will permit the carbon to burn in the manner of a hollow carbon.

5. An arcl light carbon as claimed in claim 2 characterized in that the space between the pencil and outer wall is lled with material adapted to be removed so as to 'leave a suitable Alength of the carbon near the tip. hollow to such a distance'as will permit the carbon to burn in the manner of a hollow carbon.

In witness whereof, I have hereunto signed 50 my name in the presence of two subscribing witnesses. y HERTHA AYRTON. 'Witnessesz HENRY AJLEN iPnYoR, ALFRED BEEvsLEY CAMPBELL. 

